NO. 9 NEW CAMBRIAN TRILOBITE FAUNULE — RASETTI 35 



Types.— Uolotype: U.S.N.M. 146024. Paratypes: U.S.N.M. 

 146025. 



SERRODISCUS, species tmdetermined 

 Plate 10, figure 19 



Available material. — One incomplete cephalon. 



Description. — Glabella approximately parallel-sided, rounded in 

 front, not greatly elevated, occupying with the occipital ring two- 

 thirds of the cephalic length. One pair of glabellar furrows, very 

 broad and shallow, is impressed all across the glabella. Occipital 

 furrow visible as a pair of shallow, broad depressions at the sides. 

 Occipital ring somewhat elevated medially, rounded, lacking node or 

 spine. Cheeks moderately convex, preserved only in their anterior 

 part. Preglabellar field flat, fairly extended. Border furrow shallow ; 

 border wide, flat, apparently lacking tubercles. Anterior outline of 

 cephalon unusually pointed medially. Surface of test smooth. Length 

 of cephalon 5.6 mm. 



Occurrence. — Collection cs-4. North Chatham. 



Discussion. — This cephalon cannot be referred to any described 

 species, but is too incomplete to warrant a name. The proportions 

 of the various parts are somewhat like S. speciosus, but the glabella 

 is shorter and less tapered, the entire cephalon more nearly triangular, 

 the border wider, and the occipital ring is raised at the posterior 

 margin. 



Disposition of material. — Figured specimen: U.S.N.M. 146028. 



STIGMADISCUS Rasetti, new genus 



Description. — Cephalon semielliptical, lacking lateral spines. Gla- 

 bella approximately parallel-sided, rather pointed in front, rising 

 above the downsloping cheeks, elevated in front of the occipital 

 furrow. Glabellar furrows impressed as two pairs of deep lateral pits 

 close to the axial furrow. Occipital furrow similarly deepened into a 

 pair of pits. Occipital ring well differentiated, bearing a node or 

 spine. Cephalic border narrow, defined by shallow border furrow. 

 Posterior border bearing a pair of short spines, located either about 

 halfway between the axial furrow and the genal angle, or close to 

 the genal angle. Surface of test smooth. Other parts of exoskeleton 

 unknown. 



Type species — Stigmadiscus stenometopus Rasetti, new species. 



Occurrence. — Late Lower Cambrian of New York. 



